<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <div id="app">
    <p>{{num}}</p>
  </div>
</body>
<script src="../lib/vue.js"></script>
<script>
  let myVue = new Vue({
    el: "#app",
    data:{
      num: 123,
      obj:{
        name: 123
      },
      arr:[1,2,3,4]
    },
      watch:{
        num(){
          console.log("数值变化")
        },
        obj:{
          deep:true,
          handler (){
            console.log("obj被修改了")
          }
        },
        arr(val, oldVal){
          console.log('arr被修改了', val, oldVal)
        }
      }
  })
</script>
</html>